1. Field of the Invention
The present invention relates to a focusing device of a viewing optical instrument such as an astronomical telescope.
2. Description of the Related Art
A rack-and-pinion type focusing device is generally used as a focusing device for conventional viewing optical instruments such as astronomical telescopes. In rack-and-pinion type focusing devices, a pinion is driven by rotating a focus knob to move a focus member (generally a movable tube which is movable relative to the telescope main tube) provided thereon with a rack meshing with the pinion in the optical axis direction so as to bring a distant object into focus. In this conventional type focusing device, since the focusing operation is carried out by manually rotating the focus knob, the astronomical telescope cannot stay still due to hand movement. This deteriorates the accuracy of focusing.
If the pinion is driven by a motor, the accuracy of focusing improves because the astronomical telescope is prevented from suffering from such hand movement. However, among conventional astronomical telescopes, no astronomical telescope is known to be provided with a rack-and-pinion type focusing device whose focusing operation mode can be easily switched between a manual operation mode, in which the pinion is driven manually, and a motor operation mode in which the pinion is driven by motor. Moreover, in conventional astronomical telescopes, the concept of utilizing the positional information of the aforementioned focus member via a feedback function is not known in the art.
The primary object of the present invention is to provide a focusing device of a viewing optical instrument, wherein an auxiliary unit, provided independently from the body of the viewing optical instrument, can be connected to the body of the viewing optical instrument as needed. The auxiliary unit extends the capability of a manual focusing device of the viewing optical instrument, providing the viewing optical instrument with a motor-driven focusing function or a positional information feedback function.
To achieve the object mentioned above, according to an aspect of the present invention, a viewing optical instrument is provided, including a main barrel which supports an objective optical system; a movable member for focus adjustment which is supported by the main barrel to be movable along an optical axis of the objective optical system relative to the main barrel; a focusing mechanism which drives the movable member along the optical axis; a focus knob which actuates the focusing mechanism; an auxiliary unit provided separately from the viewing optical instrument including an auxiliary mechanism which is associated with the focusing mechanism when the auxiliary unit is connected to the viewing optical instrument; and a connecting device for detachably attaching the auxiliary unit to the viewing optical instrument.
When the auxiliary unit is connected to the viewing optical instrument, the auxiliary mechanism is coupled to the focusing mechanism via a route different from a route of which the focus knob is coupled to the focusing mechanism.
Preferably, the viewing optical instrument further includes a fixed housing fixed to the main barrel, and a first mount, formed on the fixed housing, on which the auxiliary unit is mounted, the first mount having a first through hole through which part of the focusing mechanism is exposed to the outside of the viewing optical instrument.
Preferably, a cover is further provided, which is connected to the first mount when the auxiliary unit is not connected to the first mount.
Preferably, the focusing mechanism includes a rack fixed to the movable member, the rack extending parallel to the optical axis, and a first pinion which is rotatably supported to mesh with the rack. The first pinion is driven when the focus knob is operated.
The viewing optical instrument can be an astronomical telescope.
Preferably, the movable member is a movable barrel fitted in the main barrel to be movable along the optical axis of the objective optical system relative to the main barrel.
In an embodiment, the driven device includes a counter which indicates the axial position of the movable member.
In an embodiment the auxiliary unit includes a second mount which is mounted onto the first mount when the auxiliary unit is connected to the viewing optical instrument. The second mount has a second through hole through which part of the auxiliary mechanism is exposed to the outside of the auxiliary unit, and the first through hole is aligned with and the second through hole when the auxiliary unit is mounted onto the first mount.
According to another aspect of the present invention, a viewing optical instrument includes a main tube and a drawtube which is drawn out of and inserted into the main tube to focus the telescope on an object which is to be viewed through the telescope; a focusing mechanism for driving the drawtube relative to the main tube; a focus knob which actuates the focusing mechanism; an auxiliary unit provided separately from the viewing optical instrument, the auxiliary unit including a auxiliary mechanism which is associated with the focusing mechanism when the auxiliary unit is connected to the telescope; and a connecting device for detachably attaching the auxiliary unit to the telescope.
The present disclosure relates to subject matter contained in Japanese Patent Application No.11-247161 (filed on Sep. 1, 1999) which is expressly incorporated herein by reference in its entirety.